I'll give that RB kit a look. I did some more research last night and found this same creaking problem on other brembo-style calipers for Audi, Subaru, and Lotus guys.
This Lotus thread was the only one that seemed to solve the problem, which seemed to be excessive buildup of pad material between the piston and pads. He also added some anti-seize to the pads. I'm going to take the pads out again this weekend and give those specific surface a better cleaning. Fingers crossed!
FYI this Audi video perfectly captures the sound my car makes: